A presentation of student research

The effect of ambient noise is foreseen as an area of legitimate concern for future offshore renewable energy developments. Almost all aspects of the average fish life cycle involve sound in one way or another. For one, interspecies interaction involves sound in many regards (Gill 2005). Smaller fish species use sound to avoid predators, and these predators likewise use sound to seek out prey. Communication within the species is also often a sound reliant function. Species of fish that form schools use sounds as a means to locate and attract their brethren in order to join or create the schools. Sounds have proven to be a means for fish to attract mates as well. While fish are already exposed to a wide variety of existing anthropogenic noises, the effects of noise from OREDs such as wind turbines could be more harmful as a result of the large scale required for an effective clean energy farm. Loud noises, above 150 decibels, illicit startle responses from fish. The maximum noise level from wind farms during operation is between 142 DB and 153 DB for large farms (Howell 2004). This is right in the range of sound level that has proven to disturb fish.

Excessively loud sounds can permanently damage fish hearing, leaving them vulnerable to predation and hindering reproduction (Loud Noise 2003). Individual wind turbines operate with noises anywhere from 80 to 110 decibels, but studies show that again the scale of the farm dictates the level of disturbance (Gill 2005). Some species of freshwater fish are able to adapt to the unnatural noises their environment, and while this is likely also the case for some ocean species, research on the matter is limited. Studies on Goldfish showed that they experienced hearing loss to white noise above 150 DB, but the hearing ability recovered over time after the noise was removed (Popper 2004). Other tests on migratory salmon showed that fish exhibit avoidance behavior toward low frequency sounds, but may become tolerant of them after repeated exposure (Mueller 1998). Tolerance might allow the fish to cope with the ambient noise itself, but would raise the threshold of the quietest sounds they could hear and thus possibly interfere with the regular usage of sound by fish.